Measurements of electromagnetic fields in biomedical applications

Electromagnetic fields can interact with biological systems. Under some conditions, such interactions result in biological effects that may be hazardous, while in some other situations they may be beneficial and lead to some new medical applications. Examples of the latter are electromagnetically induced hyperthermia, bone healing, and nuclear magnetic resonance (NMR) imaging. To quantify and assist in understanding the interactions, it is necessary to know the intensities of electromagnetic fields. In many cases, information abut the field strengths inside exposed biological bodies is equally or even more important than that about the strength of the external exposure fields. In this context, measurements of electromagnetic fields at frequencies from a few hertz to about tens of gigahertz are very important. Some classical measurement techniques used in electromagnetics are directly, or with certain modifications, applicable to biomedical applications. However, due to special requirements, new specifically tailored techniques have had to be developed. A review of measurement methods and instrumentation for probing external and internal electric and magnetic fields as relevant to biomedical applications is given. Specific requirements, limitations of existing methods, and future needs are discussed.